Vehicle seat with cushion plate

ABSTRACT

A vehicle seat comprises a rectangular-shaped seat back frame having right and left side frames; a flexible plate member provided between the right and left side frames; a seat back cushion provided in front of the flexible plate member; a mechanism for pushing the seat back cushion to a front direction by forwardly protruding the flexible plate member that results from the flexible plate member being bent; a headrest for supporting a head of a seat occupant, wherein the headrest is forwardly movably connected to the right and left side frames via right and left link members; and a rear-end collision detecting plate disposed at a portion of the seat back frame behind the seat occupant, wherein the rear-end collision detecting plate detects rearward movement of the seat occupant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/718,309, filed Nov. 21, 2007, which is a PCT national stageentry of international patent application no. PCT/JP2005/19937, filedOct. 28, 2005, which claims the foreign priority benefit of Japanesepatent application no. JP2004-313623, filed Oct. 28, 2004. The contentsof these applications are herein incorporated by reference.

TECHNICAL FIELD

The present invention relates to a vehicle seat, and particularly to avehicle seat having a cushion plate with a pressure adjusting mechanism.

BACKGROUND

A conventional seat back cushion for a vehicle seat is resilientlysupported by means of a number of seat springs which are located betweenside frames of a seat back frame. The seat springs generally comprisezigzag springs or formed wire springs.

The degree of bending of the seat springs locally vary depending on themagnitude of load imparted. The springs located in the upper and lowerportions of the seat back frame are more bent than those located in thecentral portion of the seat back frame. Even in one spring, the centralpart of the spring is more bent than the right and left side parts ofthe spring. Thus, the degree of bending of the springs are locallyvaried. This brings about deterioration of the stability and comfort ofthe seat when a person sits on the seat.

Japanese Patent Application Laid-Open No. 11-206506 discloses astructural arrangement where an auxiliary plate, which is forwardly andrearwardly movable, is provided in connection with the cushion plate.

The auxiliary plate disclosed in Japanese Patent Application Laid-OpenNo. 11-206506 is integrally formed at the central part of the cushionplate, and the cushion plate is disposed only around the auxiliaryplate. Therefore, the cushion plate disposed around the auxiliary platefails to exhibit its function as the mechanism for resilientlysupporting the seat back cushion. This means that a load of the seatedperson is focused on the auxiliary plate and is not effectivelydispersed in the cushion plate.

Also in the conventional technique, it is difficult to provide both of apressure adjusting mechanism of the cushion plate and an active headrestmechanism for moving the headrest to the front when the vehicle rear-endcollision occurs in the seat back. In other words, the pressureadjusting mechanism lowers a sensitivity of a collision detector of theactive headrest mechanism, and hence, it is difficult to coexistentlyprovide both of the mechanisms.

SUMMARY

Accordingly, an object of various embodiments of the present inventionis to provide a cushion plate with a pressure adjusting mechanism whichis able to support the seated person while effectively dispersing theload of the seated person.

Another object is to provide a vehicle seat having a cushion plate witha pressure adjusting mechanism and an active headrest mechanism formoving the headrest to the front when the vehicle rear-end collisionoccurs.

In more detail, various embodiments of the invention provide a vehicleseat that comprises a rectangular-shaped seat back frame having rightand left side frames; a flexible plate member provided between the rightand left side frames; a seat back cushion provided in front of theflexible plate member; a mechanism for pushing the seat back cushion toa front direction by forwardly protruding the flexible plate member thatresults from the flexible plate member being bent; a headrest forsupporting a head of a seat occupant, wherein the headrest is forwardlymovably connected to the right and left side frames via right and leftlink members; and a rear-end collision detecting plate disposed at aportion of the seat back frame behind the seat occupant, wherein therear-end collision detecting plate detects rearward movement of the seatoccupant; wherein: each end portion of the rear-end collision detectingplate extends to a respective outer side of an end of the flexible platemember and is connected to a lower end portion of a respective linkmember; the flexible plate member is disposed anterior to the rear-endcollision detecting plate; an upper end of the flexible plate member isdisposed above an upper end of the rear-end collision detecting plate;and all of the rear-end collision detecting plate is positioned within aregion between the upper end of the flexible plate member and a maximumforward portion of a curve of the flexible plate member formed when theflexible plate member is bent.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings illustrate an embodiment of the invention that isdescribed in more detail below.

FIG. 1 is a perspective view showing a vehicle seat;

FIG. 2 is an exploded perspective view showing a seat back frame of thevehicle seat and basic components of an active headrest mechanism;

FIG. 3 is a perspective view showing an assembly of the components shownin FIG. 2;

FIG. 4 is a perspective view showing a state that a cushion plate and anauxiliary plate are mounted to the assembly of FIG. 3;

FIG. 5 is a side view showing a side frame of the seat back frame andthe basic components of the active headrest mechanism;

FIG. 6 is a perspective view showing the back sides of the cushion plateand the auxiliary plate;

FIG. 7 is a side view showing a relationship between a part of skeletonof a seated person and the cushion plate; and

FIG. 8 is a longitudinal sectional view showing the cushion plate andthe auxiliary plate.

DETAILED DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present invention will be described with referenceto the accompanying drawings. Referring to FIGS. 1-4, a vehicle seat 1of the present invention has a seat back 2, a seat bottom 3 and aheadrest 4 provided at the top of the seat back 2. Referring to FIGS. 2and 3, a seat back frame 5 of the seat back 2 includes a pair of sideframes 6, an upper frame 7 and a lower frame 8, and has a substantialrectangular shape.

A headrest support 10 is arranged near the upper frame 7. The support 10horizontally extends and is movable with respect to the seat back frame5. Lower parts of pillars 9 of the headrest 4 are inserted into verticalengaging parts 11 which are fixed to the headrest support 10. Thepillars 9 are vertically adjustable with the aid of the verticalengaging parts 11.

Brackets 12 are fixed to the side frames 6, respectively. The framescomprise a front projecting wall 6 b and a rear projecting wall 6 c. Anupper link or bell crank 15 is rotatably mounted to each bracket 12 by ashaft 16. Each upper link 15 includes an upper long arm 22 extendingupward and a lower short arm 23 extending downwardly and to the frontside. The upper link 15 is urged by resiliency of an upper spring 13clockwise, as shown in FIG. 5. The upper spring 13 includes a first endcoupled to the upper link 15 and a second end coupled to the side frame6. The right and left ends of the headrest support 10 are coupled to theupper arms 22, respectively. Each lower arm 23 is axially fixed to theupper part of a longitudinally extending coupling (or load transmission)rod 20 by way of a pin 21.

The upper link 15 is normally held at a position indicated by a solidline in FIG. 5 by the resiliency of the upper spring 13 or the like,whereby the headrest 4 is also held at a normal position. However, whenthe upper link 15 is rotated counterclockwise toward a positionindicated by a dotted line, the headrest support 10 forwardly moves andthe headrest 4 is pushed to the front.

A horizontally extending vehicle rear-end collision detector 25 isarranged between the side frames 6, 6. When a rear-end collision occursand the vehicle seat 1 relatively moves forward against the vehicle seatoccupant T (FIG. 7), the collision detector 25 (FIGS. 3, 4) movesrearward by being pushed by the seat occupant T. Both ends of thecollision detector 25 are coupled to lower links 26, 26 by way of pins27, 27 (also “swinging shaft”) which are axially fixed to the sideframes 6, 6 by support shafts 28, 28, via connecting members 25′, 25′respectively. The lower part of the coupling rod 20 is coupled to thelower link (link member) 26 by way of a pin 29. As shown in FIG. 5, oneend of a lower spring (biasing member) 14 is coupled to the lower link26 at a first biasing member engagement portion 26′, while the other endthereof is coupled to the side frame 6 at a second biasing memberengagement portion 6″, whereby the lower links 26 are urgedcounterclockwise. As a result, the collision detector 25 is held at anormal position, located in the front side.

When a rear-end collision occurs, the vehicle rear-end collisiondetector 25 is pushed by the seat occupant T to move rearward and toturn the lower links 26 counterclockwise in FIG. 5 and to lower thecoupling rod 20. At this time, a distance between the pin 29 and theshaft 28 is shorter than a distance between the pin 27 and the shaft 28,so that a backward movement of the collision detector 25 is efficientlytransmitted to the coupling rod 20. A downward movement of the rod 20rotates the upper link 15 counterclockwise so that the headrest support10 moves forward. The upper arm 22 of the upper link 15 is longer thanthe lower arm 23 so that the downward movement of the coupling rod 20efficiently causes the headrest support 10 to move forward. The forwardmovement of the headrest support 10 pushes the headrest 4 to the front,thereby protecting a head (neck) of the seat occupant T at the time ofthe rear-end collision.

The side frames 6 are formed with a metal plate having a predeterminedwidth as viewed in the front-and-back direction. A transmissionmechanism for transmitting a backward movement of the vehicle rear-endcollision detector 25 to the headrest support 10 is located at aposition near the side frames 6. Accordingly, a cushion 17 of the seatback 2 does not interfere with a motion of the transmission mechanism. Amechanism ranging from the collision detector 25 to the headrest support10 forms an active headrest mechanism.

A flexible plate member 30 comprises a flexible cushion plate 31 and aflexible auxiliary plate 41. The flexible cushion plate 31 is arrangedinside the seat back frame 5. The cushion plate 31 is preferably made ofsynthetic resin such as polypropylene, and is substantially a singlerectangular plate. The cushion plate 31 is attached to seat springs 32such as zigzag springs or formed wire springs at mounting portions (wireengagement portions) 31 a, 31 a′ that may include a rearward projectingportion 31 b. The seat springs 32 include at least an upper seatspring/wire member 32A and a lower seat spring 32B, the lower seatspring 32B being attached to the cushion plate 31 at a mounting portion31 a′ within a protruding portion 31 c, and to the side frame 6 at awire spring engagement portion 6 a′. The seat springs 32 horizontallyextend and are respectively coupled to the side frames 6 of the seatback frame 5 at wire spring engagement portions 6 a, 6 a′. The seat backcushion 17 is provided in front of the cushion plate 31.

When the flexible cushion plate 31 receives a load from the seatoccupant T, the cushion plate 31 moves rearward against the elasticityof the seat springs 32 and flexibly supports the seat occupant T. Thecushion plate 31 supports the seat back cushion 17 in “plane”.Therefore, the cushion plate makes the seat occupant T feel more stableand comfortable than the conventional one in which the seat back cushion17 is supported by only the seat springs 32.

An upper edge 34 of the flexible cushion plate 31, as shown in FIG. 7,is located somewhat higher than the ninth thoracic vertebra X of theseat occupant T of the average height. The center gravity of the upperbody of the seat occupant T is positioned near the ninth thoracicvertebra X. The cushion plate 31 is able to effectively support a partaround the center of gravity of the seat occupant T.

The upper seat spring 32A is selected to be at substantially the sameheight level as the ninth thoracic vertebra X or somewhat lower than it.In FIG. 7, the upper seat spring 32A is located somewhat lower than theninth thoracic vertebra X. The reason for this is that a load of theupper part of the body to the seat back cushion 17 usually acts on therearward side.

The flexible cushion plate 31 includes a lower part 33 for supporting aportion near the sacrum S of the pelvis. The lower part 33 enhances aholding property at a portion near the hip of the seat occupant T.

The vehicle rear-end collision detector 25 is located in the rear of theflexible cushion plate 31 in a state that a predetermined space ispresent therebetween. Since the cushion plate 31 takes a plate-likeshape for broadly covering the back of the seat occupant T, the flexiblecushion plate 31 receives a load of the seat occupant T on a wide areawhen a rear-end collision occurs, and moves rearwardly. The amount of arearward movement of the flexible cushion plate 31 is the largestbetween a mid portion as vertically viewed and a portion somewhat lowerthan the mid position. Therefore, the collision detector 25 ispreferably located at a mid position as vertically viewed or a positionsomewhat lower than the mid position in order to reliably receive therearward movement of the cushion plate 31. Since a width of the seatback 2 as viewed in the front-and-back direction becomes narrowerupward, it is not preferable that the collision detector 25 is locatedat an upper position on the rear side of the flexible cushion plate 31.

A flexible auxiliary plate 41 is provided between the flexible cushionplate 31 and the seat back cushion 17. Collectively, the flexiblecushion plate 31 and auxiliary plate 41 may be construed as a loadreceiving member. The auxiliary plate 41 is preferably made of syntheticresin such as polypropylene, and is substantially a single rectangularplate, which is smaller than the flexible cushion plate 31. When theauxiliary plate 41 is operated by the seat occupant T, it is bent to thefront and pushes the seat back cushion 17 forwardly, thereby adjusting acushion pressure against the seat occupant T.

The auxiliary plate 41, which has a top portion 41 a, is provided withrearward projecting upper sliders 42 and lower sliders 43. The uppersliders 42 protrude to the rear side of the flexible cushion plate 31through vertical upper slits 45 formed in the cushion plate 31. Thelower sliders 43 protrude to the rear side of the cushion plate 31through vertical lower slits 46 formed in the cushion plate 31. An upperhorizontal mounting shaft 48 is bridged between the upper sliders 42 and42, and a lower horizontal mounting shaft 49 is bridged between thelower sliders 43 and 43.

The auxiliary plate 41 is mounted to the cushion plate 31 by using themounting shafts 48 and 49. The sliders 42 and 43 are vertically slidablein the slits 45 and 46, respectively. When the upper sliders 42 aremoved downwardly and the lower sliders 43 are moved upwardly, theauxiliary plate 41 is bent to the front.

An upper U-shaped bracket 51 is rotatably mounted on the upperhorizontal mounting shaft 48. The bracket 51 includes a pair of arms 52mounted to the mounting shaft 48 and a coupling part 53 provided betweenthe arms 52. A cable head 56A of an inner cable 56 of a wire cable 55 isplaced on and secured to the coupling part 53. A lower bracket 66 isrotatably mounted to the lower horizontal mounting shaft 49. The lowerbracket 66 includes a pair of arms 67 mounted to the mounting shaft 49and a coupling part 68 provided between the arms 67. A tube head 57A ofan outer tube 57 of the wire cable 55 is placed on and secured to thelower bracket 66. The other end of the wire cable 55 is coupled to anoperation member 58 provided on the vehicle seat 1.

When the operation member 58 is operated, a distance between the cablehead 56A and the tube head 57A, i.e., a distance between the uppersliders 42 and the lower sliders 43 is adjusted. When the distancebecomes long, the auxiliary plate 41 is parallel to the flexible cushionplate 31, and when it becomes short, the auxiliary plate 41 bends toproject to the front. Thus, by operating the operation member 58, adegree of bending (forward projecting quantity) of the auxiliary plate41 can be adjusted.

The auxiliary plate 41 includes a thin part 60 for defining a curvedshape of the auxiliary plate 41. When the distance between the uppersliders 42 and the lower sliders 43 becomes short, the auxiliary plate41 is curved with respect to the thin part 60. Accordingly, the curvedshape of the auxiliary plate 41 is kept in a predetermined shape, andthe cushion pressure adjustment by the auxiliary plate 41 is madeeffective by setting the thin part 60 at the lumber part of the seatoccupant T.

A spring 61, having an upper end attaching portion 61 a for urging theupper horizontal mounting shaft 48 upwardly is provided between theupper horizontal mounting shaft 48 and the flexible cushion plate 31 (orthe upper seat spring 32A).

The flexible cushion plate 31 bends under a load from the seat occupantT and moves rearward against the elasticity of the seat springs 32, andflexibly supports the seat occupant T. The flexible cushion plate 31supports the seat back cushion 17 in “plane”. Therefore, the cushionplate makes the seat occupant T feel more stable and comfortable thanthe conventional one in which the seat back cushion 17 is supported byonly the seat springs 32.

When a physique of the seat occupant T presents an insufficient pressurefrom the seat back cushion 17, the seated person pulls the inner cable56 by operating the operation member 58 to reduce the distance betweenthe upper sliders 42 and the lower sliders 43. Then, the auxiliary plate41 protrudes forward with respect to the thin part 60, pushes the seatback cushion 17 forward to increase the cushion pressure, whereby thecushion pressure is adjusted as the seat occupant T desires.

When the auxiliary plate 41 is curved by the operation member 58, thecushion pressure is changed. Since the auxiliary plate 41 and theflexible cushion plate 31 are in overlapping relation, the load by theseat occupant T that the auxiliary plate 41 receives is directlydispersed into the flexible cushion plate 31 as a single large plate.Accordingly, the good stability and comfort of the seat back cushion 17are not lost.

When a rear-end collision occurs, the flexible cushion plate 31 greatlymoves rearward by the load from the seat occupant T to come into contactwith the vehicle rear-end collision detector 25 and to move it backward.In turn, the lower links 26, in FIG. 5, rotate counterclockwise to lowerthe coupling rod 20. The downward movement of the coupling rod 20 turnsthe upper links 15 counterclockwise to move the headrest support 10 tothe front. As a result, the headrest 4 pushed to the front to protectthe head (neck) of the seat occupant T against the impact by therear-end collision.

In this case, the distance between the pin 29 and the shafts 28 isshorter than that between the pins 27 and the shafts 28. Accordingly,the lower links 26 efficiently transmits the rearward movement of thecollision detector 25 to the coupling rod 20. Since the upper arms 22 ofthe upper links 15 are longer than the lower arms 23, the downwardmovement of the coupling rod 20 is efficiently transmitted to theheadrest support 10. Therefore, the forward movement of the headrest 4is satisfactorily secured.

Since the cushion plate 31 is shaped like a plate broadly covering theback of the seat occupant T, it reliably receives the rearward movementof the seat occupant T at the time of the rear-end collision in a broadarea to reliably transmit the rearward movement of the seat occupant Tto the collision detector 25.

When the auxiliary plate 41 is bent by the operation member 58, thecushion pressure is changed. Since the flexible cushion plate 31 isshaped like a plate broadly covering the back of the seat occupant T,and receives the load from the seat occupant T in a dispersing manner,the change of the cushion pressure by the auxiliary plate 41 does notsubstantially move the positions of the flexible cushion plate 31 andthe collision detector 25. Accordingly, the relative position of thecushion plate 31 to the collision detector 25 is retained and the changeof the cushion pressure by the auxiliary plate 41 does not substantiallyinterfere with the function of the active headrest mechanism.

1. A vehicle seat comprising: a rectangular-shaped seat back frame having right and left side frames; a flexible plate member provided between the right and left side frames; a seat back cushion provided in front of the flexible plate member; a mechanism for pushing the seat back cushion to a front direction by forwardly protruding the flexible plate member that results from the flexible plate member being bent; a headrest for supporting a head of a seat occupant, wherein the headrest is forwardly movably connected to the right and left side frames; and a rear-end collision detecting plate disposed at a portion of the seat back frame behind the seat occupant and connected to the seat back frame via right and left link members, wherein the rear-end collision detecting plate detects rearward movement of the seat occupant; wherein: each end portion of the rear-end collision detecting plate extends to a respective outer side of an end of the flexible plate member and is connected to a lower end portion of a respective link member; the flexible plate member is disposed anterior to the rear-end collision detecting plate; an upper end of the flexible plate member is disposed above an upper end of the rear-end collision detecting plate; and all of the rear-end collision detecting plate is positioned within a region between the upper end of the flexible plate member and a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 2. The vehicle seat according to claim 1, further comprising: a spring member having an upper end attachment portion for attaching the spring member to the flexible plate member, wherein the upper end attachment portion is disposed above the upper end of the rear-end collision detecting plate.
 3. The vehicle seat according to claim 1, further comprising: a spring member having an upper end and a lower end, wherein: the upper end of the spring member is attached to the flexible plate member, and the lower end of the spring member is disposed above the maximum forward portion of the curve of the flexible plate member.
 4. The vehicle seat according to claim 1, further comprising: a spring member having an upper end and a lower end, wherein: the upper end of the spring member is attached to the flexible plate member and disposed above the upper end of the rear-end collision detecting plate; and the lower end of the spring member is disposed above the maximum forward portion of the curve of the flexible plate member.
 5. The vehicle seat according to claim 1, further comprising: an upper portion of the seat back frame extending in a horizontal direction; and a lateral member that is generally parallel to the upper portion of the seat back frame and supports a pillar of the headrest; wherein: the lateral member is disposed opposite to the upper end of the flexible plate member and is larger in length in a lateral direction than the flexible plate member; the rear-end collision detecting plate is disposed below and generally parallel to the lateral member; and the upper end of the flexible plate member is disposed between the lateral member and the upper end of the rear-end collision detecting plate.
 6. The vehicle seat according to claim 5, wherein: all of each link member is positioned within a region between the lateral member and the maximum forward portion of the curve of the flexible plate member.
 7. The vehicle seat according to claim 5, further comprising: a wire member supported by the seat back frame between the side frames; and a wire engagement portion mounted at a back of the flexible plate member to engage the wire member; wherein: the wire engagement portion is disposed above the upper end of the rear-end collision detecting plate and disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction; and all of each link member is positioned within a region between the lateral member and the maximum forward portion of the curve of the flexible plate member.
 8. The vehicle seat according to claim 1, further comprising: a wire member supported by the seat back frame between the side frames; wherein: the flexible plate member is provided with a wire engagement portion to engage the wire member; and the wire engagement portion is disposed above the upper end of the rear-end collision detecting plate.
 9. The vehicle seat according to claim 8, wherein: the wire engagement portion is disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction.
 10. The vehicle seat according to claim 8, wherein: the wire engagement portion is mounted at a back of the flexible plate member and disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction.
 11. The vehicle seat according to claim 1, further comprising: a spring member having an upper end attachment portion for attaching the spring member to the flexible plate member, wherein: the upper end attachment portion is disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction.
 12. The vehicle seat according to claim 11, wherein: the rear-end collision detecting plate is disposed at a position that avoids a region opposite to a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 13. The vehicle seat according to claim 11, further comprising: an upper portion of the seat back frame extending in a horizontal direction; and a lateral member that is generally parallel to the upper portion of the seat back frame and supports a pillar of the headrest; wherein: the lateral member is disposed opposite to the upper end of the flexible plate member and is larger in length in a lateral direction than the flexible plate member; the rear-end collision detecting plate is disposed below and generally parallel to the lateral member; and the upper end of the flexible plate member is disposed between the lateral member and the upper end of the rear-end collision detecting plate; all of each link member is positioned within a region between the lateral member and a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 14. A vehicle seat comprising: a rectangular-shaped seat back frame having right and left side frames; a wire member supported by the seat back frame between the side frames; a flexible plate member mounted to the wire member; a seat back cushion provided in front of the flexible plate member; a mechanism for pushing the seat back cushion to a front direction by forwardly protruding the flexible plate member that results from the flexible plate member being bent; a wire engagement portion provided on the flexible plate member to engage the wire member; a headrest for supporting a head of a seat occupant, wherein the headrest is forwardly movably connected to the right and left side frames; and a rear-end collision detecting plate disposed at a portion of the seat back frame behind the seat occupant and connected to the seat back frame via right and left link members, wherein the rear-end collision detecting plate detects rearward movement of the seat occupant; wherein: each end portion of the rear-end collision detecting plate extends to a respective outer side of an end of the flexible plate member and is connected to lower end portion of the link members; the flexible plate member is disposed anterior to the rear-end collision detecting plate; an upper end of the flexible plate member is disposed above an upper end of the rear-end collision detecting plate; and the wire engagement portion is disposed above the upper end of the rear-end collision detecting plate.
 15. The vehicle seat according to claim 14, further comprising: a spring member having an upper end attachment portion for attaching the spring member to the flexible plate member, wherein: the upper end attachment portion is disposed above the upper end of the rear-end collision detecting plate.
 16. The vehicle seat according to claim 14, further comprising: a spring member having an upper end and a lower end, wherein: the upper end of the spring member is attached to the flexible plate member, and the lower end of the spring member is disposed above a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 17. The vehicle seat according to claim 14, further comprising: a spring member having an upper end and a lower end, wherein: the upper end of the spring member is attached to the flexible plate member and disposed above the upper end of the rear-end collision detecting plate; and the lower end of the spring member is disposed above a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 18. The vehicle seat according to claim 14, further comprising: an upper portion of the seat back frame extending in a horizontal direction; and a lateral member that is generally parallel to the upper portion of the seat back frame and supports a pillar of the headrest; wherein: the lateral member is disposed opposite to the upper end of the flexible plate member and is larger in length in a lateral direction than the flexible plate member; the rear-end collision detecting plate is disposed below and generally parallel to the lateral member; and the upper end of the flexible plate member is disposed between the lateral member and the upper end of the rear-end collision detecting plate.
 19. The vehicle seat according to claim 18, wherein: all of each link member is positioned within a region between the lateral member and a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 20. The vehicle seat according to claim 18, wherein: the wire engagement portion is mounted at a back of the flexible plate member and disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction: and all of each link member is positioned within a region between the lateral member and a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 21. The vehicle seat according to claim 14, further comprising: a spring member having an upper end attachment portion for attaching the spring member to the flexible plate member, wherein: the upper end attachment portion is disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction.
 22. A vehicle seat comprising: a rectangular-shaped seat back frame having right and left side frames; a wire member supported by the seat back frame between the side frames; a flexible plate member mounted to the wire member; a seat back cushion provided in front of the flexible plate member; a mechanism for pushing the seat back cushion to a front direction by forwardly protruding the flexible plate member that results from the flexible plate member being bent; a headrest for supporting a head of a seat occupant, wherein the headrest is forwardly movably connected to the right and left side frames; a rear-end collision detecting plate disposed at a portion of the seat back frame behind the seat occupant and connected to the seat back frame via right and left link members, wherein the rear-end collision detecting plate detects rearward movement of the seat occupant; and protruding portions provided on right and left side portions of an upper portion of the flexible plate member and protruding outward; wherein: each end portion of the rear-end collision detecting plate extends to a respective outer side of an end of the flexible plate member and is connected to a lower end portion of a respective link member; each of the protruding portions includes a wire engagement portion to engage the wire member; the flexible plate member is disposed anterior to the rear-end collision detecting plate; an upper end of the flexible plate member is disposed above an upper end of the rear-end collision detecting plate; and the wire engagement portion is disposed above the upper end of the rear-end collision detecting plate.
 23. The vehicle seat according to claim 22, further comprising: a spring member having an upper end attachment portion for attaching the spring member to the flexible plate member, wherein the upper end attachment portion is disposed above the upper end of the rear-end collision detecting plate.
 24. The vehicle seat according to claim 22, further comprising: a spring member having an upper end and a lower end, wherein the upper end of the spring member is attached to the flexible plate member, and the lower end of the spring member is disposed above a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 25. The vehicle seat according to claim 22, further comprising: a spring member having an upper end and a lower end, wherein: the upper end of the spring member is attached to the flexible plate member and disposed above the upper end of the rear-end collision detecting plate; and the lower end of the spring member is disposed above a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 26. The vehicle seat according to claim 22, further comprising: an upper portion of the seat back frame extending in a horizontal direction; and a lateral member that is generally parallel to the upper portion of the seat back frame and supports a pillar of the headrest; wherein: the lateral member is disposed opposite to the upper end of the flexible plate member and is larger in length in a lateral direction than the flexible plate member; the rear-end collision detecting plate is disposed below and generally parallel to the lateral member; and the upper end of the flexible plate member is disposed between the lateral member and the upper end of the rear-end collision detecting plate.
 27. The vehicle seat according to claim 26, wherein: all of each link member is positioned within a region between the lateral member and a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 28. The vehicle seat according to claim 26, wherein: the wire engagement portion is mounted at a back of the flexible plate member and disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction: and all of each link member is positioned within a region between the lateral member and a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 29. The vehicle seat according to claim 22, further comprising: a spring member having an upper end attachment portion for attaching the spring member to the flexible plate member, wherein: the upper end attachment portion is disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction.
 30. A vehicle seat comprising: a rectangular-shaped seat back frame having right and left side frames; a wire member supported by the seat back frame between the side frames; a flexible plate member mounted to the wire member; a seat back cushion provided in front of the flexible plate member; a mechanism for pushing the seat back cushion to a front direction by forwardly protruding the flexible plate member that results from the flexible plate member being bent; a wire engagement portion provided on the flexible plate member to engage the wire member; a headrest for supporting a head of a seat occupant, wherein the headrest is forwardly movably connected to the right and left side frames; an upper portion of the seat back frame extending in a horizontal direction; and a lateral member that is generally parallel to the upper portion of the seat back frame and supports a pillar of the headrest; and a rear-end collision detecting plate disposed at a portion of the seat back frame behind the seat occupant and connected to the seat back frame via right and left link members, wherein the rear-end collision detecting plate detects rearward movement of the seat occupant; wherein: each end portion of the rear-end collision detecting plate is connected to a respective lower end portion of the link members; the flexible plate member is disposed anterior to the rear-end collision detecting plate; the lateral member is disposed opposite to an upper end of the flexible plate member and is larger in length in a lateral direction than the flexible plate member; the rear-end collision detecting plate is disposed below the lateral member; and the upper end of the flexible plate member is disposed between the lateral member and an upper end of the rear-end collision detecting plate.
 31. The vehicle seat according to claim 30, wherein: the whole of the rear-end collision detecting plate is positioned within a region between the upper end of the flexible plate member and a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 32. The vehicle seat according to claim 30, further comprising: a spring member having an upper end attachment portion for attaching the spring member to the flexible plate member, wherein the upper end attachment portion is disposed above the upper end of the rear-end collision detecting plate.
 33. The vehicle seat according to claim 30, further comprising: a spring member having an upper end and a lower end, wherein: the upper end of the spring member is attached to the flexible plate member, and the lower end of the spring member is disposed above a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 34. The vehicle seat according to claim 30, further comprising: a spring member having an upper end and a lower end, wherein: the upper end of the spring member is attached to the flexible plate member and disposed above the upper end of the rear-end collision detecting plate; and the lower end of the spring member is disposed above a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 35. The vehicle seat according to claim 30, further comprising: a spring member that biases the link member; wherein: the spring member is disposed between an upper end of the lateral member and a lower end of the rear-end collision detecting plate.
 36. The vehicle seat according to claim 30, further comprising: a spring member that biases the link member; wherein: one end of the spring member is engaged with an end portion of the link member and the other end of the spring member is engaged with an end portion of the side frame in a front-to-back direction.
 37. The vehicle seat according to claim 30, further comprising: a spring member that biases the link member; wherein: the spring member is disposed between an upper end of the lateral member and a lower end of the rear-end collision detecting plate; and one end of the spring member is engaged with an end portion of the link member and the other end of the spring member is engaged with an end portion of the side frame in a front-to-back direction.
 38. The vehicle seat according to claim 30, wherein: the link member is swingably supported by a support fixed to the side frame; and the supported shaft is disposed below the lateral member and above the rear-end collision detecting plate.
 39. The vehicle seat according to claim 30, wherein: all of each link member is positioned within a region between the lateral member and a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 40. The vehicle seat according to claim 30, wherein: the wire engagement portion is disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction.
 41. The vehicle seat according to claim 30, wherein: the wire engagement portion is mounted at a back of the flexible plate member and disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction.
 42. The vehicle seat according to claim 30, wherein: the wire engagement portion is mounted at a back of the flexible plate member and disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction: and all of each link member is positioned within a region between the lateral member and a maximum forward portion of a curve of the flexible plate member formed when the flexible plate member is bent.
 43. The vehicle seat according to claim 30, further comprising: a spring member having an upper end attachment portion for attaching the spring member to the flexible plate member, wherein: the upper end attachment portion is disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction.
 44. A vehicle seat comprising: a rectangular-shaped seat back frame having right and left side frames; a wire member supported by the seat back frame between the side frames; a flexible plate member mounted to the wire member; a seat back cushion provided in front of the flexible plate member; a mechanism for pushing the seat back cushion to a front direction by forwardly protruding the flexible plate member that results from the flexible plate member being bent; a wire engagement portion provided on the flexible plate member to engage the wire member; a headrest for supporting a head of a seat occupant, wherein the headrest is forwardly movably connected to the right and left side frames; a rear-end collision detecting plate disposed at a portion of the seat back frame behind the seat occupant and connected to the seat back frame via right and left link members, wherein the rear-end collision detecting plate detects rearward movement of the seat occupant; and a spring member having an upper end attachment portion for attaching the spring member to the flexible plate member; wherein: each end portion of the rear-end collision detecting plate extends to a respective outer sides of and end of the flexible plate member and is connected to a lower end portion of a respective link member; the flexible plate member is disposed anterior to the rear-end collision detecting plate; an upper end of the flexible plate member is disposed above an upper end of the rear-end collision detecting plate; the wire engagement portion is disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction; and the upper end attachment portion of the spring member is disposed at a position that avoids a region opposite to the rear-end collision detecting plate in a front-to-back direction. 